How to read only new content in VSTO Outlook MailItem body?

I've written a little C# VSTO add-in for Outlook 2003 that reads the body of emails as they are being sent, looking for certain words. It's working right now to do this:

if (currentItem.Body.Contains("text to search for"))

... but that checks the entire email body, not just the new message being sent.

Is there anyway to have Outlook just check the contents of the new message being sent, and so ignore the older email chain that might be in there too?

These messages could be in any format (HTML, Rich Text, Plain Text) and may or may not have any earlier messages chained in. This is just a productivity tool for me, so any hack that works is worth considering here.

For the record, the solution I decided worked best for me was to simply check for a line starting with "FROM:", Mikael suggested. I stop searching for my text as soon as that is found. That's been working just fine for me for a while now.

Thanks for the responses and ideas, everyone.

Here's my code for reference:

Private Sub Application_ItemSend(ByVal Item As Object, Cancel As Boolean)
Dim theLine As String
Dim aBody()
Dim bFound As Boolean
Dim ctr As Long
aBody = Array(Split(Item.Body, vbNewLine))
bFound = False
For ctr = 0 To UBound(aBody(1))
theLine = aBody(1)(ctr)
If InStr(theLine, "From:") > 0 Then
Exit For
End If
If InStr(UCase(theLine), "ATTACH") > 0 Then
bFound = True
End If
Next
If bFound Then
If Item.Attachments.Count < 1 Then
Dim ans As Integer
ans = MsgBox("Do you really want to send this without any attachments?", vbYesNo)
If ans = 7 Then
Cancel = True
Exit Sub
End If
End If
End If
End Sub

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